Drone Transport of Deceased-Donor Kidney Grafts Between Two French Hospitals Before Transplantation: a Pilot Safety Study

Background. Cold ischemia time (CIT) is the main modifiable determinant of delayed graft function (DGF) and of medium- and long-term kidney graft survival; each additional hour of CIT increases the risk of graft failure and mortality. The French Ministerial Plan for Organ and Tissue Procurement and Transplantation 2022-2026 set a target mean CIT of 10 hours or less for kidney transplantation and explicitly identified drone transport of grafts as a priority lever, whereas national median CIT for deceased-donor kidney transplantation remains around 14-15 hours. Conventional transport modes (road, rail, chartered or commercial flights) are exposed to traffic, timetables, airport procedures and coordination constraints, and dedicated non-commercial flights carry a non-negligible accident risk. Unmanned aircraft systems (UAS) are already used in national medical logistics networks (blood products, vaccines, laboratory samples) and in hospital corridor programmes in the United Kingdom. In 2019, the University of Maryland Medical Center performed the first kidney transplantation after drone transport of the graft, with stable temperature, vibration levels lower than in commercial aviation and no macroscopic or histological alteration. In Europe, work on organ transport by drone remains limited to feasibility and logistic modelling studies, without reported human transplantation.

Preliminary work. Nantes University Hospital (kidney transplant unit, 160-180 kidney transplantations per year) and the organ procurement coordination of CHD Vendée have collaborated for more than ten years; Nantes receives 15 to 20 kidneys procured in La Roche-sur-Yon each year. On 2 June 2024, both centres performed an experimental drone transport of a porcine kidney on the exact route planned for this study (La Roche-sur-Yon to Nantes), with full recording of flight parameters (temperature, vibrations, flight time), absence of macroscopic graft alteration and confirmation of graft function after auto-transplantation following bilateral nephrectomy. The study also aims to determine whether drone transport reduces graft exposure to shocks and thermal variations before any extension to other transplant centres.

Design. Prospective, bicentric, open-label, non-randomised, single-arm pilot study including 5 kidney transplant recipients. The procurement centre is CHD Vendée (La Roche-sur-Yon); the transplantation centre is Nantes University Hospital. The study is a first step towards a larger study (letter of intent submitted to the French PREPS programme, DGOS, December 2025).

Transport chain. After standard procurement, the kidney is packaged in a refrigerated container clinically approved for graft transport, using either static cold storage or hypothermic machine perfusion (both modes may be used in the study). The container is flown by an autonomous vertical take-off and landing fixed-wing drone (RigiTech Eiger: maximum take-off mass 21 kg, maximum payload 3 kg / 15 L, cruise speed about 104 km/h, operational wind limits 12 m/s in multirotor phase and 15 m/s in fixed-wing phase; ballistic parachute with independent failsafe unit, redundant navigation sensors, dual command-and-control links). Flights are operated beyond visual line of sight by the specialised operator Delivrone within the European 'specific' category framework, on the basis of a SORA risk assessment (SAIL II) and an operational authorisation from the French civil aviation safety directorate (DSAC), within a dedicated medical air corridor between La Roche-sur-Yon and Nantes (about 62 km as the crow flies; 75 to 88 km along the planned flight path).

Data recorded. Donor characteristics (age, sex, donor type, anthropometry, cause of death, cardiovascular history, cardiac arrest, last-hour diuresis, creatinine, proteinuria, haematuria, vasopressors); complete transport timeline (ground transfer before flight, loading, flight, ground transfer after landing); temperature and three-axis vibrations measured by a sterile sensor in contact with the graft; perfusion machine alarms if applicable; weather and corridor data and any technical incident; pre-implantation biopsy (acute glomerular, interstitial, tubular, vascular and peritubular capillary lesions, infarction or haemorrhage); recipient and surgical data (cold and warm ischemia, number of arteries, ureteral stent, time on waiting list and on dialysis); early graft function during the first post-operative week (dialysis sessions, primary non-function, serum creatinine, estimated glomerular filtration rate); follow-up visits at D10-D30, M1-M3 and M3-M12 (biology, urinalysis, ultrasound as clinically indicated, uro-vascular complications, maintenance immunosuppression, return to dialysis, graft nephrectomy, death). All clinical data derive from routine care.

Missions not completed by drone. If the drone cannot take off (adverse weather, winds above operational limits, regulatory unavailability or saturation of the corridor, technical issue) or if the mission is interrupted in flight (automatic return to base or landing in a predefined safe area), the graft is immediately transferred by conventional transport according to standard pathways, with no loss of chance for the recipient. In that case the recipient is not included in the drone-transport analysis, but every planned mission, including delayed, cancelled or aborted missions, is systematically documented and analysed to identify limiting factors.

Statistical analysis. Analyses are descriptive. The primary outcome is expressed as the proportion of recipients without DGF with its exact 95% confidence interval (Clopper-Pearson). Quantitative secondary outcomes are described (mean, standard deviation, median, minimum, maximum) with individual presentation by patient and by mission. No comparative or confirmatory analysis, no significance threshold, no interim analysis and no imputation of missing data are planned. The analysis population comprises all recipients transplanted with a graft effectively transported by drone (as treated); the transport safety analysis includes all planned drone missions.

Budget impact. Transport costs of the study grafts, based on invoices, will be compared with mean transport costs observed in 2024 and 2025 (between Nantes and CHD Vendée, and between these centres and other national centres), from the hospital perspective, with a projection of the annual financial impact of deploying drone transport at Nantes University Hospital.